In some devices, confidential information is stored using content protection, for example, encrypted with a password which the user of the device enters via a user input interface. However, in other devices, for example those without a suitable user input interface, confidential information may be stored without any protection, that is, transparently, or “in the clear”. If this device is stolen, the confidential information may be revealed by probing the memory in which the confidential information is stored.
In general, wireless communication is insecure and susceptible to attacks. Cryptographic techniques may be employed to secure a wireless communication link. In symmetric-key systems (also known as “secret-key systems”), a single, common cryptographic key is stored by two communication devices. In public-key systems (also known as “public-private pair systems”), each communication device stores its own private key and freely distributes its own public key. If the symmetric key or either or both of the private keys is not kept secret, the security of the communication between the two devices is compromised. A hostile third party with knowledge of the secret may impersonate one or both of the devices.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity.